The present invention relates to an environmental control system for a home or building. Specifically, the invention relates to an environmental control system which is capable of the automatic adjustment of the humidistat setpoint so as to avoid condensation on windows or walls or both.
Typically the environmental conditions within a building are maintained during the heating season by the use of a furnace or heat pump to heat indoor air and a humidifier to provide moisture to the indoor air. In regions where the outdoor air temperature varies significantly such as due to the changing seasons, the amount of humidity provided by the humidifier needs to be adjusted periodically in relation to changes in the outdoor air temperature. If the humidity level is not adjusted as the temperature changes, condensation can build up on the inside of walls, windows, and other parts of the building. This is especially crucial during the winter months when the outdoor air temperature gets colder since the possibility of condensation is inversely related to the outdoor temperature. As the outdoor air temperature drops it becomes much easier to build up condensation on the windows and the exterior walls of a building. This condensation can create many problems including the windows becoming non-transparent and damage to the wood and construction materials of the walls, ceilings or both. Consequently, it is desirable to lower the humidity level within the controlled space in order to prevent condensation on the windows, outside walls, ceiling, or any combination thereof.
various means have been used to try to control the humidity level within a home in relation to outdoor air temperatures. Specifically, humidity sensors or frost sensors have been placed on windows and have been used to sense the presence of condensation. Once condensation is detected the humidity level of the building is then adjusted to eliminate the condensation.
Another method of avoiding condensation within the house is to place a temperature sensor in the heat supply duct of the furnace. This sensor measures the load on the heating system. Once the heating system load is known, the humidity level within the house can then be adjusted. A device utilizing this method is shown in the Honeywell H403 humidity control described in U.S. Pat. No. 3,279,699.
All of the aforementioned methods of humidity control have required the use of additional sensors and in some cases complex circuitry to achieve the required goals. Additionally, installation of these products may be complicated and at times very difficult.